The present invention relates to an electric drive unit for a water-bearing domestic appliance. The invention also relates to a domestic appliance having at least one hydraulic pump and an electric drive unit.
In a water-bearing domestic appliance, in particular a dishwasher, it is common for a plurality of types of hydraulic pumps to be used. For example, a hydraulic pump is provided as a circulating pump for use during the washing process and another hydraulic pump as a drain pump for pumping out the water on completion of a wash program or program section. Such hydraulic pumps are disposed in the sump of a dishwasher and are generally supplied with system voltage from the domestic (mains) system. This type of hydraulic pump is also known, for example, in the field of washing machines, which generally have both circulating pumps and drain pumps.
DE 101 39 928 A1 discloses a dishwasher pump drive in which a DC voltage motor with permanent magnet rotor and with sensor commutator for rotor-position-dependent polarity reversal of the magnetomotive force of the field winding is used as a pump motor. The field circuit can be supplied from the rectifier provided on a circuit board of the operating circuit, said rectifier enabling the DC motor to be operated from an AC voltage system. For each field winding, the two-phase DC motor has two inverse coil sections which are alternately supplied with current via a changeover switch. A commutator sensitive to the polarity of the multipole permanent magnet rotor mounted in the air gap as a wet rotor specifies which of the two field windings is to be instantaneously subjected to magnetomotive force.
DE 39 13 639 A1 describes a modular wiring arrangement in domestic dishwashers which uses a common distribution circuit board and supplies all the small loads with 42V protective voltage, thereby enabling the wiring arrangement to be clearly structured and inexpensive low-voltage components to be implemented. All the leads to the loads such as heater and pump motors are connected to corresponding make-contacts and supplied with system voltage after actuation of a main control switch. On the load side of a distribution circuit board, an isolating transformer is provided whose secondary side has a rated voltage of max. 42V. This is to be regarded as a safety extra-low voltage and in turn supplies the control side and therefore the small loads via the main control switch.
In DE 103 39 130 A1, a domestic appliance such as a washing machine or dishwasher with circulation of liquid is described in which the drive motors for the hydraulic pumps are activated such that at least one of the two pumps can be connected to a control unit for open-loop and/or closed-loop motor control, the central component of the control unit being a computer with a processor and the control unit being able to be used as the central open- and closed-loop control unit of the appliance. It assumes the function of control unit for two hydraulic pumps, in particular a circulating pump and a drain pump. There is additionally provided a plurality of sensors on a connection side of the computer which are used to detect one or more machine parameters. For example, one of said sensors is implemented as a load sensor for detecting a pump load or more specifically the pump input current, a number of actuators then being actuated by the control unit as a function of the sensor data. DC voltage motors, for example, can be used for pump drive, thereby eliminating the hitherto occasionally produced hum caused by the operating voltage ripple. A DC voltage of 42 volts, for example, or lower can be used in the low voltage range, particular safety advantages being able to be achieved in this connection. With the large number of sensors or actuators connected to the computer, drive control is comparatively complex and must provide different supply systems for the different sensors and actuators and for the pump drive.